• Proceedings of the KSRS Conference
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• 2004.10a
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• pp.522-525
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• 2004

Interferometry SAR (InSAR) is a technique to generate topographic map from complex data pairs observed by antennas at different locations. However, to obtain topographic information using InSAR is difficult task because it requires series of complicated process including phase unwrapping and precise recovery of the SAR geometry. Especially, accuracy of the DEM (Digital Elevation Model) produced by repeat pass single SAR pair could be influenced by atmospheric effect. Recently, a new InSAR technique to improve accuracy of DEM has been introduced that utilizes low resolution DEM with a number of SAR image pairs. The coarse DEM plays an important role in reducing phase unwrapping error caused by layover and satellite orbit error. In this study, we implemented DInSAR (Differential InSAR) method which combines low resolution DEMs and ERS tandem pair images. GTOPO30 DEM with 1km resolution, SRTM-3 DEM with 100m resolution, and DEM with 10m resolution derived from 1:25,000 digital vector map were used to investigate feasibility of DInSAR. The accuracy of the DEMs generated both by InSAR and DInSAR was evaluated.

• Proceedings of the KSRS Conference
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• v.1
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• pp.247-249
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• 2006

The objective of this study is to detect a inter-tidal topographic change in a decade. Waterline extraction is a one of widely used method to generate digital elevation model (DEM) of tidal flat using multi-temporal optical data. This method has been well known that it is possible to construct detailed topographic relief of tidal flat using waterlines In this study, we generated two sets of tidal flat DEM for the southern Ganghwado. The DEMs showed that the Yeongjongdo northern tidal flat is relatively high elevation with steep gradients. The Ganghwado southern tidal flat is relatively low elevation and gentle gradients. To detect the morphologic change of tidal flat during a decade, we compared between early 1990's DEM and early 2000's DEM. Erosion during a decade is dominant at the west of southern Ganghwado tidal flat, while sedimentation is dominant at the wide channel between the southern Ganghwado and Yeongjongdo tidal flats. This area has been commonly affected by high current and sedimentation energy. Although we are not able to verify the accuracy of the changes in topography and absolute volume of sediments, this result shows that DEM using waterline extraction method is an effective tool for long term topographic change estimation.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.454-458
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• 2007

Nonpoint source (NPS) pollution is a serious problem causing the degradation of soil and water quality. Concentrated overland flow is the primary transport mechanism for a large amount of NPS pollutants from hillslope areas to downslope areas in a watershed. In this study, a soil erosion model, nLS model, to identify transitional overland flow regions (i.e., ephemeral gully head areas) was developed using the kinematic wave overland flow theory. Spatial data, including digital elevation models (DEMs), soil, and landcover, were used in the GIS-based model algorithm. The model was calibrated and validated using gully head locations in a large agricultural watershed, which were identified using 1-m aerial photography. The model performance was better than two previous approaches; the overall accuracy of the nLS model was 72 % to 87 % in one calibration subwatershed and the mean overall accuracy was 75 to 89 % in four validation subwatersheds, showing that the model well predicted potential transitional erosion areas at different watersheds. However, the user accuracy in calibration and validation was still low. To improve the user accuracy and study the effects of DEM resolution, finer resolution DEMs may be preferred because DEM grid is strongly sensitive to estimating model parameters. Information gained from this study can improve assessing soil erosion process due to concentrated overland flow as well as analyze the effect of microtopographic landscapes, such as riparian buffer areas, in NPS control.

• Korean Journal of Geomatics
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• v.2 no.2
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• pp.131-137
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• 2002

The digital photogrammetric products have been increasingly used as an accurate foundation for representing information associated with infrastructure management. The technological advances in merging raster and vector data within the framework of GIS have allowed for the inclusion of DTMs and digital orthophotos with vector data and its associated attributes. This study addresses not only generating DEMs and digital orthophotos but producing three dimensional building models from aerial photos of an urban area by employing the digital photogrammetric technology. DEMs and digital orthophotos were automatically generated through the process of orientations, image matching and so on, and then the practical problems, which must be solved especially in applying to urban areas, were considered. The accuracy of produced digital orthophotos was derived by using check points. Also three dimensional visualization imagery, which is useful in the landform analysis, and 3D building models were produced. Digital photogrammetric products would be used widely not only as GIS framework data layers by using the GIS link function which links attribute and image information in the database for applying to infrastructure management and but as geospatial data for especially 3D GIS in urban areas.

• Proceedings of the KSRS Conference
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• 2002.10a
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• pp.524-529
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• 2002

In this paper, we report the development of two DEM (digital elevation model) generation algorithms over urban areas from an IKONOS stereo pair. One ("EpiMatch") is originally developed for SPOT images and modified for IKONOS images. It uses epipolar geometry for accurate DEM generation. The other is based on graph-cut algorithm in 3D voxel space. This algorithm is believed to work better on height discontinuities than EpiMatch. An IKONOS image pair over Taejon city area was used for tests. Using ground control points obtained from differential GPS, camera model was set up and stereo matching applied. As a result, two DEMs over urban areas were produced. Within a DEM from EpiMatch small houses appear as small "cloudy" patches and large apartment and industrial buildings are visually identifiable. Within the DEM from graph-cut we could achieve better height information on building boundaries. The results show that both algorithms can generate DEMs from IKONOS images although more research is required on handling height discontinuities (for "EpiMatch") and on faster computation (for "Graph-cut").

• Korean Journal of Radiology
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• v.20 no.1
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• pp.34-49
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• 2019

Conventional transcatheter arterial chemoembolization (c-TACE) is a widely used first-line palliative treatment for patients with unresectable hepatocellular carcinoma (HCC). Despite the effectiveness of c-TACE, to date, technique and procedure scheduling has not yet been standardized. Drug-eluting microspheres (DEMs) were therefore introduced to ensure more sustained and tumor-selective drug delivery for permanent embolization. These DEMs can load various drugs and release them in a sustained manner over a prolonged period. This approach ensures the delivery of high concentrations of chemotherapeutic agents to tumors, without increasing systemic concentrations, and promote tumor ischemia and necrosis. This review summarizes the recent advances in the use of DEM-TACE to treat HCC.

• Journal of Korean Society for Geospatial Information Science
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• v.15 no.4
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• pp.103-109
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• 2007

Ortho images and Digital Elevation Model (DEM) have been applied in various fields. It is necessary to acquire Ground Control Points (GCPs) for processing high resolution satellite images. However surveying GCPs require many time and expense. This study was performed to investigate whether GCPs automatically extracted from ortho images and DTED Level 2 can be applied to sensor modeling for high resolution satellite images. We analyzed the performance of the sensor model established by GCPs extracted automatically. We acquired GCPs by matching satellite image against ortho images. We included the height acquired from DTED Level 2 data in these GCPs. The spatial resolution of the DTED Level 2 data is about 30m. Absolution accuracy of this data is below 18m above MSL. The spatial resolution of ortho image is 1m. We established sensor model from IKONOS images using GCPs extracted automatically and generated DEMs from the images. The accuracy of sensor modeling is about $4{\sim}5$ pixel. We also established sensor models using GCPs acquired based on GPS surveying and generated DEMs. Two DEMs were similar. The RMSE of height from the DEM by automatic GCPs and DTED Level 2 is about 9 m. So we think that GCPs by DTED Level 2 and ortho image can use for IKONOS sensor modeling.

• Journal of Korean Society for Geospatial Information Science
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• v.19 no.1
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• pp.21-28
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• 2011

Site conditions affect the magnitude of loss due to geologic hazards including, but not limited to, earthquakes, landslides and liquefaction. Reliable geologic loss estimation system requires site information which can be achieved by GIS-based method using geologic or topographic maps. Slope data derived from DEM can be an effective indicator for classifying the site conditions. We studied and discussed the effect of different DEM resolutions in the site classification. We limited the study area to the south-eastern Korea and used two different resolutions of DEMs to observe discrepancies in the site classification results. Largest discrepancy is observed in the areal coverage of site class C(very dense soil and soft rock) and E(soft soil). Comparison of results shows that more areas are classified as site class B(general rock) or E(soft soil) when we use higher resolution DEM. The comparison also shows that more areas are classified as site class C or D(stiff soil) using lower resolution DEM. The comparison of results using resampled DEMs with different resolutions shows that the areal coverage of site class B and E decreases with decreasing resolutions. On the contrary, areal coverage of site class C and D increase with decreasing resolutions. Loss estimation system can take advantage of higher-resolution DEMs in the area of rugged or populated to obtain precise local site information.

• Korean Journal of Remote Sensing
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• v.18 no.4
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• pp.221-231
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• 2002

In this study we applied a DEM generation algorithm developed in-house to satellite images at various resolution and discussed the results. We tested SPOT images at l0m resolution, EOC images at 6.6m and IKONOS images at 1m resolution. These images include the same urban area in Daejeon city. For camera model, we used Gupta & Hartley's(1997) DLT model for all three image sets. We carried out accuracy assessment using USGS DTED for SPOT and EOC and 23 check points for IKONOS. The assessment showed that SPOT DEM had about 38m RMS error, EOC DEM 12m RMS error and IKONOS DEM 6.5m RMS error. In terms of image resolution, SPOT and EOC DEM error corresponds to 2∼4 pixels where as IKONOS DEM error 6∼7pixels. IKONOS DEM contains more errors in pixels. However, in IKONOS DEM, individual buildings, apartments and major roads are identifiable. All three DEMs contained errors due to height discontinuity, occlusion and shadow. These experiments show that our algorithm can generate urban DEM from 1m resolution and that, however, we need to improve the algorithm to minimize effects of occlusion and building shadows on DEMs.

• The Safety technology
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• no.141
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• pp.18-21
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• 2009

부산지역 전력수요의 약 65%를 담당하고 있는 한국남부발전(주) 부산천연가스발전본부는 2007년 11월부터 전사 안전시스템 선진화 시범사업장으로 선정되어 안전시스템 선진화의 초석이 되는 발전소로 거듭나고 있다. 안전보건관리시스템인 KOSHA 18001과 공정안전관리(PSM)을 기본으로 2009년 5월 도입된 재난안전관리시스템(DEMS), 행동교정프로그램인 ASA 제안안제도뿐 아니라 발전사로는 처음으로 신 작업안전시스템을 도입하여 위험성평가와 키락킹(Key-Locking)으로 인적실수나 오작동에 의한 안전사고를 사전에 방지하는 철저한 안전경영시스템 정착시켜 언제, 어디서 발생할지 모르는 안전 및 재난사로에 대비하고 있다.